Effect of Bacillus subtilis supplementation and dietary crude protein level on growth performance and intestinal morphological changes of meat type chicken

A study was conducted to evaluate the potential of Bacillus subtilis-based probiotic to decrease crude protein (CP) requirement of broiler chicks. Growth performance, carcass, and meat quality characteristics, digestive tract development and ileal digestibility of CP were investigated using a total of 720 one-day-old commercial mixed sex broiler chicks. The recommended CP (CP100) or 2% below the recommended CP (CP98) were tested in the presence or absence of 0.2 g/kg of B. subtilis (0.8×109 cfu/g) in a 2×2 factorial arrangement of treatments in a completely randomized design. Broiler chicks were randomly assigned to 4 dietary treatments with 6 replicate pens per treatment and 30 broiler chicks per pen. Basal diets of starter, grower, and finisher were formulated according to the recommendations for commercial broiler chicks. Bacillus subtilis supplementation did not affect growth performance of broiler chicks. However, dietary CP level decreased (P<0.05) body weight gain and feed efficiency. Broiler chicks supplemented with B. subtilis had a greater (P<0.05) fillet weight with no differences observed for other carcass characteristic measurements. Adding B. subtilis had no effect on the meat quality measurements; however, dietary CP reduced (P<0.05) meat water holding capacity. Also, B. subtilis deepened (P<0.05) jejunum crypts and improved (P<0.05) ileal CP digestibility. The results obtained from this study have enough evidence to assume that B. subtilis supplementation had beneficial effect on jejunum morphology and can reduce the adverse effect of dietary CP reduction. It may be concluded that the alteration in gastrointestinal morphological characters because of probiotic use was positively reflected on better CP ileal digestibility and the improved feed efficiency.